Ársrit Fiskifélags Íslands - 01.01.1933, Blaðsíða 78

76
within certain limits. The size-class in net-fish, which the nets take
in quantity, is larger, compared with the corresponding group
in the longline-fish, than any other group in the net-fish, compared
with the corresponding group in the longline-fish. If we compare
the figures in the columns »net« and »lóð« we find that the nets
take the class-size of 105—109 cm. in quantity, and therefore we
put the figures 12 = 100 in column »Ióð a« and the figure 29'
= 100 in the column »net b«, and work out all the other figures
in each column in proportion to the percentages of 12 and 29
respectively, and thus we get the figures in the columns »lóð a«
and »net b«. If you work out each figure in the column »net b«
in percentage of the corresponding figure in the column »lóð a«*
one gets the figures in column X = b : a • 100, and they show how
great a percentage of every class the nets take. The figures in.
the column 100 :X are reciprocal with the figures in the column,
X = b : a 100, and therefore a length-distribution graph for net-fisb
can be made similar to the one for longline-fish, by multiplying"
the figures in the former scale by the figures in the column
X: 100. Then you will get the figures in the last column. If no'
fish had escaped from the nets, that is, if they had workedi
quantitatively, then 300 square metres of net would represent a
longline of 1000 hooks.
The otoliths of the catfish serve to give an indication of agef
at least in young fish. The age of a few catfish was investigated
through the otoliths, with the result shown in table 53.
Hr = females. Hœ — males.